New freezing chamber with refrigeration storage

ABSTRACT

A freezing chest or freezing shelf comprising a compressor, heat exchangers and a heat storage arrangement with a heat storage material having a crystallization temperature above the temperature of the evaporator and below the maximum permissible temperature of the goods to be refrigerated. The heat storage material is arranged in containers formed from thin walled plastics, and the containers are disposed between the container of the goods to be refrigerated and the insulating layer, and are in contact with the wall of the former over approximately half the total surface. Further, the containers of the heat storage material have recesses for the evaporator tubes which are equally in contact with the wall of the container of the goods.

iJnited States Patent 11 1 Laing 1451 July 24,1973

[ NEW FREEZING CHAMBER WITH REFRIGERATION STORAGE 22 Filed: July 12,1971

211 Appl. No.: 161,738

[30] Foreign Application Priority Data 3,161,031 12/1964 Flannery 62 5303,545,230 12 1970 Morse 2,603,071 5 1952 Kalhoefer 62/457 FOREIGNPATENTS OR APPLICATIONS 665,731 1 1952 Great Britain 62/439 1,185,811 31970 Great Britain 530 Primary ExaminerWilliam .l. Wye Attorney-WillisH. Taylor, Robert McKay et al.

[57] ABSTRACT A freezing chest or freezing shelf comprising acompressor, heat exchangers and a heat storage arrangement with a heatstorage material having a crystallization temperature above thetemperature of the evapo rator and below the maximum permissibletemperature of the goods to be refrigerated. The heat storage materialis arranged in containers formed from thin walled plastics, and thecontainers are disposed between the container of the goods to berefrigerated and the insulating layer, and are in contact with the wallof the former over approximately half the total surface. Further, thecontainers of the heat storage material have recesses for the evaporatortubes which are equally in contact with the wall of the container of thegoods.

14 Claims, 5 Drawing Figures NEW FREEZING CHAMBER WITH REFRIGERATIONSTORAGE THE PRIOR ART It is known to provide storage bodies in freezingchests, from which heat of crystallization is withdrawn duringoperation, so that for example in the event of electric power failure anadequately low temperature is maintained for prolonged periods withoutthe operation of the refrigeration plant. Eutectic cryohydrates whichare liquid at normal temperature while crystallizing during compressoroperation, are used as storage masses. These masses are accomodated incontainers which are at the same time traversed by the heat exchangertubes of the coolant evaporator.

The advantages to be expected are, however, counteracted by appreciabledisadvantages, so that refrigeration storage apparatus has not caught onin this field, because it was found that all cryohydrates these areeutectic systems consisting of ionogenic compounds and water experiencea large change of density as they crystallize, so that the walls of thecontainers are subjected to large alternating mechanical stresses. Ithas more ever been found that the substances which crystallize in thecourse of refrigeration operation frequently no longer work in theappropriate temperature ranges, even after only a few month ofoperation. The reason for this is that the seed crystals added for thepurpose of preventing supercooling of the storage mass and also theingredients of the eutectic of higher specific gravity collect on thefloor of the vessel, so that either the supercooling which is preventedduring normal operation by seed crystals uniformly distributed throughthe storage mass is no longer prevented, i.e., that the temperature ofcrystallization drops to lower values, or that the eutectic temperatureis no longer reached by reason of a change in the weight ratio of theingredients forming a eutectic, i.e., that the temperature ofcrystallization changes in the direction of higher values.

A further disadvantage of known solutions consists in that theevaporator tubes are surrounded by the storage mass. Thereby the heattransfer between the evaporator tubes and the wall of the container forthe goods to be refrigerated is made considerably worse, so that newlyintroduced such goods require a substantially longer period forfreezing.

SUMMARY OF THE INVENTION The invention relates to storage bodies whichare not subject to the aforesaid disadvantages. According to theinvention the storage mass container consists of plastics sheets whichare sufficiently deformable at least for compensating the variation indensity, which form resilient hollow vessels by welding alongpredetermined seams and, if desired, also spots, in which the storagemass is enclosed. Preferably the double walled sheet is provided overthe entire exterior surface of the container for the goods to berefrigerated, so that the mean required thickness of the layer ofstorage mass amounts to only a few millimeter. By means of thisarrangement, the high grade heat contact between the evaporator tubesand container for the goods to be refrigerated is not adverselyaffected. The metallic wall of the container for the goods to berefrigerated serves not only the purpose of a heat conduit for heat fromthe said goods and from the insulation, but also for conducting the heatfrom the double walled vessel with the storage mass.

Homogeneous mixtures, e.g. methanol water, are used as the storage mass.The storage may, however, also, in a manner known per se, consist ofmeltable eutectic mixtures. In accordance with the invention, this masshas then seed crystals, whose position is fixed by a substance providinga supporting structure, e.g., a gel-forming mixture additive, added toit in a uniform spatial distribution. In accordance with the invention,the storage body is arranged between the wall of the container for thegoods to be refrigerated facing the said goods and the elasticallydeformable insulating layer consisting of foamed plastics. Thereby themetallic wall of the container for the goods to be refrigerated, whichis in good heat conductive communication with the evaporator tubes, isutilized at the same time for heat distribution between the evaporatortubes of not directly adjacent regions of the cooling body andfurthermore for fixing the storage bodies. The first sheet which issecured to the metallic wall of the container for the goods to berefrigerated by an adhesive maintains its position duringcrystallization which entails volumetric expansion. The change indensity causes a displacement of the second wall, which bounds theelastic insulating layer. Since the mean thickness of the layer ofstorage mass amounts to only a few millimeters, when the entire surfaceof the container for the goods to be refrigerated is coated with thestorage body described, the movement only has the order of magnitude of1 millimeter. The storage body is preferably suspended by being securedby an adhesive to the wall of the container for the goods to berefrigerated, the regions between the evaporator tubes preferably beingfilled in. It is sufficient to provide temporary fixing or adhesion,since the storage bodies are held between the evaporator tubes afterfoaming of the insulating layer by the adaptation of its shape to thespaces between the evaporator tubes.

As a result of the melt being thickened by a substance providing asupporting structure, the invention avoids ageing of the storage massand the latter becoming ineffective, since the seed crystals, salt andwater remain in isotropic distribution and thus at an adequately smallrelative spacing. At the same time hydrostatic pressures in the lowerregions of the container are prevented, since the thickened liquidbehaves similarly to a solid body. By using plastics sheet for storagemass containers and the arrangement between the rigid wall of thechamber containing the goods to be refrigerated and the insulation,non-permissible deformation of the material is prevented. Since all thesuitable storage masses have considerably lower heat conductivity in theliquid phase than in the crystalline phase, the storage mass which hasbeen protected against heat transfer convection by the substance formingthe supporting structure, acts as additional insulation when heatedabove the temperature of crystallization.

In order that damage to the refrigeration storage device as a result ofdamage to the thin walled sheets does not result in loss of storagecapacity, the invention provides for the subdivisionof the storage massvessel into a large number of independent individual chambers, bywelding seams on the sheets. Thereby, in the event of damage, aproportion of the total storage capacity amounting to only a few percentis lost.

It has been found that, by the use of suitable storage masseshereinafter described, extraordinarily small layer thicknesses of, forexample, 8 mm result in storage capacities which permit a bridgingperiod of many hours, for example, in the event of electric powerfailure.

The invention provides, as a special further instance of itsapplication, the combination of the storage bodies with a refrigerationplant, whose rating is such that the refrigeration effect required inthe course of a day can be produced basically during the off-peak nighttime period. This has the advantage that the charging takes place onlyduring the cool hours of night, in which the Carnot efficiency is betterthan during the day, so'that during normal operation less energy isconsumed. At the same time the mechanical efficiency of the installationincreases with an increase in the size of the refrigeration plant, whichprovides further saving. The invention preferably provides the uniformdistribution of the storage mass over all vertical walls. Thereby aconsiderable reduction in energy with optimum heat transfer conditionsis created, which permits rapid freezing even in the case of largequantities to be refrigerated, e.g. the sudden demand for refrigerationof large quantities of goods during fruit harvest or slaughtering.

Suitable storage masses comprise alcohol-water mixtures, e. g.methanol-H O as well as cryohydrates, whose thermodynamically activeconstituent consists of 37 NaNO or 40 (NH SO or 23 NaCl or 42 NI-I NOall the said percentages being by weight. Suitable thickening substancescomprise aerosiles of highpolymer swellable hydrocarbons, particularlyalginates.

The disadvantage of storage mass vessels of large area consists in thepossibility of loss of the substance in view of the vapor permeabilityof the majority of plastics sheets, particularly for the sheet which isnot secured by adhesive to the wall of the container for the goods to berefrigerated. The invention therefore provides a multi-layer sheet, inwhich one layer consists of a metal, e.g., aluminum.

The arrangement according to the invention is suitable not only for thecontainers for the goods to be refrigerated of freezing chest, but alsofor refrigerators and particularly freezing shelves of refrigerators.

The invention will be explained in greater detail with reference to thefollowing description of the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a section view of arefrigerated compartment constructed according to the invention;

FIG. IA is an enlarged section of a portion of FIG. 1 illustrating thepositioning of a heat storage element with respect to the inner wall ofthe compartment;

FIG. 2 is a graph illustrating change of temperature of a compartmentconstructed according to the invention with respect to time; I

FIG. 3 is a side view of a further embodiment of a heat storage elementconstructed according to the invention; and

FIG. 3A is an enlarged sectional view of a portion of FIG. 3illustrating the attachment of the heat storage element to an inner wallofa refrigerated compartment.

DETAILED DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates diagrammaticallyin section a refrigerated compartment 1 having an outer wall member 1'and an inner wall member 3. Evaporator tubes 2 which are in good heatconductive communication with the inner wall member 3 extend spirallyaround the compartment. The tubes 2 contain a coolant which is adaptedto be circulated therethrough in order to cool the interior of thecompartment. Between wall 3 and insulation material 4, heat storageelements 5 are arranged which are surrounded by a thin flexible tube 6.The thin flexible tube is connected to the wall 3, e.g., by means of anadhesive, along the seam 7 and is held in this position by shapeadaptation after foaming of the insulation 4. The thin flexible tube 6is sqeezed together at regular intervals and welded up along the seam 8to form individual containers 9.

FIG. 2 shows the heating curve 20 for refrigerated compartments withouta storage mass and 21 for freezing chests with a storage mass. Thehorizontal region 23 corresponds to the temperature of crystallizationof the storage mass. This lies above the temperature of evaporation 24.of the coolant circulated in the evaporator tubes and below thetemperature 25 which must not be exceeded from the point of view ofmaintenance of the storability of the goods to be refrigerated. Onlyafter completion of the crystallization, does the temperature increasealong the curve 26.

FIG. 3 shows a further embodiment of the invention. The storage elementhere consists of a coherent sleeve, whose wall 30 facing the insulationextends outside the evaporator tubes 2 along an approximately levelplane, while the wall 31 facing the wall 3 has bulges 32, which enclosethe evaporator tubes. The sleeve shown is in tended for compartment 1for goods to be refrigerated, as shown in FIG. 1, and is laid around thevertical edges of the compartment along the fold lines 33/33 34/34,35/35 and preferably secured to protrusions 37 by means of eyes 36 andthe straps 39' and 39" are held together by means of eyes 38 and a cord.

Preferably, the heat storage material may comprise alcohol watermixtures, for example methanol-H O as well as cryohydrates thethermodynamically active constituent of which may comprise either 37%.NA N0 40% (NI-L0 S0 23% Na Cl, or 42% NI-I NO all of said percentagesbeing by weight. In addition, thickening substances may be added to theheat-storage material to provide a supporting structure, as for example,aerosiles of high-polymer swellable hydrocarbons, particularlyalginates, or long-fiber silicon dioxide-hydrate crystals.

I claim:

1. A refrigerated compartment having an outer wall member, an inner wallmember spaced from said outer wall member, insulation material betweensaid wall members, a plurality of evaporator tubes positioned betweensaid members for cooling said compartment, and a coolant circulating insaid tubes; the improvement comprising including a heat storage elementbetween said wall members where said element has a plurality ofindividual flat containers joined end to end posi tioned between andcontacting said insulation material and said inner wall, the heatstorage material in said containers having a crystallizing temperatureabove the temperature of evaporation of said coolant and below themaximum permissible working temperature of said compartment, and saidtubes being positioned along the side edges of said containers.

2. A refrigerated compartment according to claim 1 wherein saidcontainers are formed from thin flexible tubes.

3. A refrigerated compartment according to claim 1 wherein the heatstorage element comprising the containers joined end to end is spirallywound around the compartment and between said tubes.

4. A refrigerated compartment according to claim 1 wherein saidcontainers are in addition joined side to side along their edges to forma container sheet.

5. A refrigerated compartment according to claim 4 wherein the sheet ispositioned along the vertically extending inner walls of saidcompartment.

6. A refrigerated compartment according to claim 1 wherein said heatstorage material comprises a watermethanol mixture.

7. A refrigerated compartment according to claim 1 wherein the heatstorage material includes in addition a thickner substance to provide asupporting structure to said material.

8. A refrigerated compartment according to claim 7 wherein said thicknercomprises long fiber siliconedioxide hydrate crystals.

9. A refrigerated compartment according to claim 7 wherein the heatstorage material comprises ionogenic compounds and water and having inaddition seed crystals uniformly distributed in the storage materialwherein said thickner substance prevents the crystals from segregatingout of the storage material.

10. A refrigerated compartment according to claim 1 wherein the storagematerial comprises a cryohydrate of approximately 42 percent by weightof Nl-l NO 11. A refrigerated compartment according to claim 1 whereinsaid storage material comprises a cryohydrate of approximately 37percent by weight of NA N0 12. A refrigerated compartment according toclaim 1 wherein the storage material comprises a cryohydrate ofapproximately 40 percent by weight of (NI-m S0 13. A refrigeratedcompartment according to claim 1 wherein the storage material comprisesa cryohydrate of approximately 23 percent by weight of Na Cl.

14. A refrigerated compartment according to claim 1 wherein said heatstorage element comprises a water vapor impermeable sheet of multi-layerconstruction with one of said layers comprising a metal.

1. A refrigerated compartment having an outer wall member, an inner wallmember spaced from said outer wall member, insulation material betweensaid wall members, a plurality of evaporator tubes positioned betweensaid members for cooling said compartment, and a coolant circulating insaid tubes; the improvement comprising including a heat storage elementbetween said wall members where said element has a plurality ofindividual flat containers joined end to end positioned between andcontacting said insulation material and said inner wall, the heatstorage material in said containers having a crystallizing temperatureabove the temperature of evaporation of said coolant and below themaximum permissible working temperature of said compartment, and saidtubes being positioned along the side edges of said containers.
 2. Arefrigerated compartment according to claim 1 wherein said containersare formed from thin flexible tubes.
 3. A refrigerated compartmentaccording to claim 1 wherein the heat storage element comprising thecontainers joined end to end is spirally wound around the compartmentand between said tubes.
 4. A refrigerated compartment according to claim1 wherein said containers are in addition joined side to side alongtheir edges to form a container sheet.
 5. A refrigerated compartmentaccording to claim 4 wherein the sheet is positioned along thevertically extending inner walls of said compartment.
 6. A refrigeratedcompartment according to claim 1 wherein said heat storage materialcomprises a water-methanol mixture.
 7. A refrigerated compartmentaccording to claim 1 wHerein the heat storage material includes inaddition a thickner substance to provide a supporting structure to saidmaterial.
 8. A refrigerated compartment according to claim 7 whereinsaid thickner comprises long fiber silicone-dioxide hydrate crystals. 9.A refrigerated compartment according to claim 7 wherein the heat storagematerial comprises ionogenic compounds and water and having in additionseed crystals uniformly distributed in the storage material wherein saidthickner substance prevents the crystals from segregating out of thestorage material.
 10. A refrigerated compartment according to claim 1wherein the storage material comprises a cryohydrate of approximately 42percent by weight of NH4NO3.
 11. A refrigerated compartment according toclaim 1 wherein said storage material comprises a cryohydrate ofapproximately 37 percent by weight of NA NO3.
 12. A refrigeratedcompartment according to claim 1 wherein the storage material comprisesa cryohydrate of approximately 40 percent by weight of (NH4)2 SO4.
 13. Arefrigerated compartment according to claim 1 wherein the storagematerial comprises a cryohydrate of approximately 23 percent by weightof Na Cl.
 14. A refrigerated compartment according to claim 1 whereinsaid heat storage element comprises a water vapor impermeable sheet ofmulti-layer construction with one of said layers comprising a metal.